1. Field of the Invention
This invention relates to a truss shoe for use with a threaded rod and, more particularly, to a truss shoe having a threaded passageway to receive an end portion of the threaded rod; the truss shoe having a stop member spaced from an exit end of the threaded passageway to pass the end of the threaded rod past the exit end of the passageway for full thread engagement of the threaded passageway.
2. Discussion of the Presently Available Technology
Truss-type mine roof supports are well known in the art of supporting the roof of an underground passageway, such as a mine passage. A basic truss system includes one or more threaded rods extending horizontally the width of the mine passage adjacent the roof and connected at their ends to anchor bolts, which extend at an angle adjacent the ribs of the passage into the rock strata over a solid pillar. The rods are tensioned and vertical components of compressive forces are transmitted into the rock strata over the solid pillars, as opposed to the unsupported rock strata immediately above the passage.
With this arrangement, a truss system shifts the weight of the rock strata from over the mined-out passage back onto the pillars. Conventionally, holes are drilled into the mine roof at a 45° angle from the horizontal adjacent to the mine rib so that the holes extend into the supported rock strata over a pillar.
Once the holes are drilled at an angle into the strata over the pillars at the rib line, anchor bolts are inserted into the drilled holes and are secured in place using mechanical expansion shell assemblies and/or a resin made from a mixture of a resin component and an epoxy component. Before the bolts are inserted in the drilled holes, truss shoes are positioned on the bolt at the emergent end of the bolt from the hole. As the bolts are securely anchored in the drilled holes, the bearing surfaces of the truss shoes are compressed into engagement with the mine roof.
For an uneven mine roof or a roof having severely potted areas, the truss shoe preferably has sufficient bearing surface to contact the mine roof so that the truss shoe is correctly positioned for engagement with the horizontal truss members. Once the truss shoes are securely positioned at the mine roof adjacent the ribs, the horizontal truss members are assembled and connected to the truss shoes. Horizontal truss members are tightened to a predetermined tensioning load so that the weight of the rock strata over the mined-out area beneath the roof can shift along the horizontal truss members upwardly into the solid rock strata over the pillars at the rib line.
The truss hardware is connected under tension to the truss shoes that are held tightly against the mine roof by the anchored angle bolts. A wide variety of truss hardware is commercially available to form a truss system between the anchored angle bolts. For example and not limiting to the discussion, U.S. Pat. No. 7,261,494 (hereinafter also referred to as “USPN '494”) and U.S. Pat. No. 8,057,128 (hereinafter also referred to as “USPN '128”), both of which are assigned to FCI Holdings Delaware, Inc., disclose a cable truss system including a pair of truss shoes, a pair of inclined bolts, and a truss assembly. In general, the truss shoes of USPNs '494 and '128 include a bolt receiving end portion to receive the bolt that attaches the truss shoe to the ceiling or roof, and an opposite cable receiving and retaining end portion to receive an end of a cable to secure the cable to the truss shoe. The cable receiving and retaining end portion includes a tapered passageway for receiving a wedge or cone-shaped retention assembly.
The retention assembly is secured in the passageway by a washer (USPN '494) or a locking tube (USPN '128). The truss shoes of USPNs '494 and '128 are acceptable for use with truss systems that connect the truss shoes with cables, but, as can be appreciated by those skilled in the art, they are not used with truss systems that interconnect the truss shoes with threaded rods.
Truss shoes are available for use with truss systems connecting the truss shoes with threaded rods; however, the truss shoes that are interconnected by threaded bars have limitations. By way of illustration and not limited thereto, a stop member is provided at the exit end of a threaded passageway of the truss shoe. The stop member prevents the end of the threaded rod from passing through the threaded passageway, thereby preventing the threaded passageway of the truss shoe from being fully threaded on the threaded rod.
As can be appreciated by those skilled in the art, it would be advantageous to provide a truss shoe designed to permit a threaded rod to pass through the exit end of a threaded passageway of the truss shoe to provide full thread engagement of the threaded passageway by the threaded rod.